IEC 62541-5:2020

Overview

IEC 62541-5:2020 - OPC Unified Architecture, Part 5: Information Model defines the standardized Information Model for OPC UA servers. It describes the Nodes (types and instances) that make up a Server’s AddressSpace, effectively defining the AddressSpace of an empty OPC UA Server. This third edition (2020) is a technical revision of the 2015 edition and introduces new data types, methods and modelling concepts while expanding diagnostics and authentication support.

Key topics and requirements

• AddressSpace and Nodes: Standardized definitions for ObjectTypes, VariableTypes, ReferenceTypes, DataTypes and EventTypes that servers use to expose data and metadata.
• Server, Diagnostics and Capabilities: Standard ServerType, ServerDiagnostics and SessionDiagnostics objects to support monitoring, diagnostics and operational metadata.
• New data types (2020): Adds Union, Decimal, OptionSet, DateString, TimeString, DurationString, NormalizedString, DecimalString, AudioDataType for richer data modelling.
• Methods and Subscription features:
  • RequestServerStateChange - method to request server state transitions.
  • SetSubscriptionDurable - method to set a Subscription to persistent (durable) mode.
  • ResendData - method for requesting resending of subscription data.
• User Authentication and Role model: Annex F introduces a Role Information Model for user authentication and role configuration.
• Selection Lists and Audio support: New VariableType for SelectionList and AudioVariableType to support UI/voice-related data.
• Finite State Machine enhancements: Optional properties to expose available states and transitions.
• Session-less metadata: UrisVersion property for ServerType to support session-less service calls.
• Temporary file concept: Allowing servers to create temporary files for read/write operations (concept added in C.4).

Practical applications and who uses this standard

IEC 62541-5:2020 is essential for:

• OPC UA server developers implementing a compliant AddressSpace and standard Node types.
• System integrators and automation engineers building interoperable industrial control and SCADA systems.
• IIoT architects designing device-agnostic data models and persistent subscription workflows.
• Cybersecurity and operations teams leveraging standardized diagnostics, session and role information for monitoring and auditing.
• Vendors of edge devices, PLCs, HMIs and historians needing standardized data encoding (new data types) and subscription persistence.

Practical uses include device and asset modelling, diagnostics and troubleshooting, robust subscription/resend for intermittent networks, role-based access configuration, and richer data representation (dates, decimals, audio).

Related standards

• Part of the IEC 62541 (OPC UA) series - consult other OPC UA parts for core services, security, transport and encoding to implement end-to-end compliant systems.

Keywords: IEC 62541-5:2020, OPC UA Information Model, AddressSpace, OPC Unified Architecture, OPC UA server, Node, Subscription, User Authentication, SelectionList, AudioDataType.